In order to check the thickness of elongate measurement objects, e.g. long timbers or panel-shaped material to be measured, it is known to provide a measuring system which is characterized by at least one measuring roller which is held above the measurement object and can be moved in the direction towards same. The zero setting of the measuring roller which is operatively connected to a pneumatic drive is formed by means of a reference plane, on which lies the measurement object and along which said measurement object can be moved at a defined speed. For its part, the measuring roller is also operatively connected to a measuring transducer, by means of which the displacement path of said measuring roller can be represented by a corresponding electrical signal.
The measuring procedure in the case of this known measuring system is performed in such a manner that the measuring roller is moved out from its withdrawn position above the measurement object in the direction of said object and brought into contact therewith, after the moving measurement object has arrived at a position below the measuring roller. However, in dependence upon the advance speeds of the measurement object on the one hand and the measuring roller on the other hand, it is not possible as a result to record the thickness of a starting region of the measurement object. Furthermore, the measuring roller is withdrawn starting from its position rolling on the surface of the measurement object, before the end of the measurement object is reached. This limitation at the beginning and the end of the measuring path on the measurement object was adapted inter alia to avoid causing any mechanical damage to the measuring system.
In order to improve the manner in which the measuring systems are protected from mechanical destruction measuring devices are currently used, in which a run-in ramp is provided. For this purpose, a run-in ramp is provided which is mounted on its end so as to be able to pivot about an axis in parallel with a reference plane. This run-in ramp is operatively connected at its free end facing away from its articulation to a measuring roller which by means of running rollers on both sides is supported on the inner side of this ramp and passes slightly through the base region thereof.
By reason of the measurement object which abuts against the underside of the base region of the run-in ramp, said run-in ramp is pivoted, wherein during the course of further advance movement the measuring roller finally moves into position against the surface of the measurement object. In dependence upon the advance speed and also upon the comparatively long lever arm between, on the one hand, the articulation point of the run-in ramp and, on the other hand, the measuring roller, extraordinarily high acceleration moments are produced for the measuring roller and above all the elements of the measuring systems which are functionally downstream of the measuring roller. In order to avoid vibration problems which arise due to an acceleration of the run-in ramp, there is provided a control, which is allocated to the pneumatic drive of the measuring roller, with the proviso that a counter force is developed at an early stage which suppresses excessive vibration. However, the disadvantage in this case is that the acceleration moments which are to be compensated are dependent both upon the advance movement of the measurement object and also upon its thickness.
The purpose of this known measuring system is to obtain the most complete information possible on the thickness of the measurement objects—as seen in the longitudinal direction thereof—wherein the measurement objects are guided through the measuring system at a defined advance speed and at different mutual end-side spaced intervals. One essential feature of these known measuring systems is that each time a measurement object has been passed through by means of the said pneumatic drive, the measuring roller is moved either to a withdrawn position or to a zero setting. The periods of time available for these considerable deflection movements turn out to be comparatively short in dependence upon the advance speed of the measurement objects and the mutual spaced intervals between them and consequently these periods must be concluded at a correspondingly high speed and with rapid reverse-control procedures. In addition to high material stress, this can also lead to considerable noise development. As a result, these conditions restrict the advance speed of the measurement objects.